Open column groups with the default overwrite configuration, true.
A simpler solution, avoiding the additional search of the primary cursor,
clear/restore the overwrite flag before/after the initial insert, and use
the error from the primary insert call as before.
Hold the checkpoint lock while syncing the file contents in LSM.

This avoids corruption caused by racing application and LSM checkpoints.
In LSM hold the checkpoint lock before discarding a handle.
Merge branch 'develop' into column-group-overwrite-config
Use a blind insert in the primary of tables with no indices.
refs #667
Merge pull request #668 from wiredtiger/lsm_checkpoint_lock

Hold the checkpoint lock when manipulating handles in LSM.
Merge pull request #667 from wiredtiger/column-group-overwrite-config

Have table cursors do blind updates on column groups where possible.
Cleanup, move the checkpoint lock inside __lsm_discard_handle.
Avoid a deadlock in LSM between the schema lock and the checkpoint lock.

refs #668